The present invention relates to a modified ballast converter, and more particularly to a ballast converter with a power factor and current crest factor correction.
Referring to FIGS. 1(a) and (b), a typical ballast converter is used to initialize a gas discharge lamp 4, wherein the ballast converter comprises a electrical utility power line 1, a rectifier 2, and a high frequency power converter 3. The high frequency power converter 3 further comprises a switching circuit 31 and a resonance circuit 32, wherein the resonance circuit 32 is coupled between the gas discharging lamp 4 and the ballast converter.
The most important purpose for designing the ballast converter is to approach optimum power quality, such as the power factor (PF), the total harmonic distortion (THD), and the current crest factor (CCF). According to the prior art, there are many different modified methods to make a ballast converter approach optimum power quality. As examples, FIG. 1(a) depicts a valley fill ballast converter with spike reducing and FIG. 1(b) depicts a valley fill ballast converter with a high frequency current feedback. However, when the valley fill ballast converter with a high frequency current feedback is operated at an 220 volt input voltage, the 30xcx9c70 kHz switch frequency and the output power of 80 watts, wherein the PF, THD and CCF are at the values of 0.95, 31%, and 2.1 respectively. On the other hand, when the valley fill ballast converter with the high frequency current feedback is operated at an 120 volt input voltage, the 30 kHz switch frequency and the output power of 64 watts, wherein the PF, THD and CCF are at the values of 0.93, 36%, and 1.7 respectively. Accordingly, a ballast converter of the prior art has to add a lot of devices to improve the electric effect and that must increase the complexity of the circuit, the energy loss of all devices, and the cost of the ballast converter.
Hence, the present invention improves the prior art and provides a ballast converter with a power factor and current crest factor correction.
It is one object of the present invention to provide a ballast converter with power factor and current crest factor correction for improving the electrical power quality.
It is another object of the present invention to provide a ballast converter with a power factor and current crest factor correction for reducing the complexity of the circuit, the energy loss of all devices, and the cost of the ballast converter.
According to the present invention, A ballast circuit with a power factor and crest factor correction electrically connected to an power source for providing an input voltage comprises: a rectifier electrically connected to the power source for rectifying the input voltage so as to provide a first voltage at a pair of DC supply terminals; a power converter electrically connected to the rectifier for converting the first voltage into a highfrequency output voltage so as to provide a load with an electrical energy; and a valley fill circuit electrically connected with an output end of the power converter and the DC supply terminals, wherein the power converter charges the valley fill circuit for storing energy while the value of the first voltage is larger than a predetermined value, the valley fill circuit provides the first voltage with a supplementary energy while the value of the first voltage is lower than the predetermined value, and the predetermined value is adjustable by the valley fill converter circuit.
Certainly, the power converter can be an inverter.
Certainly, the first voltage can be a DC voltage.
Preferably, the valley fill circuit further comprises: a first inductor having one end electrically connected with the output end of the power converter; a first diode having a anode end electrically connected with the other end of the first inductor; a first energy-storing capacitor having one end electrically connected with a cathode end of the first diode and the other end electrically connected with the ground; and a second diode having a anode end electrically connected with the cathode end of the first diode and a cathode end electrically connected with one of the DC supply terminals.
Preferably, the ballast converter further comprises a self-excited transformer, wherein one end of a primary winding is electrically connected with the output end of the power converter and the other end of the primary winding is electrically connected with the load for detecting a current of an output end of the power convert.
Preferably, the power convert further comprises: a first transistor electrically connected with one of the DC supply terminals; a second transistor electrically connected with the first transistor, wherein a connecting point of the two transistors is an output end of the power convert; a first resistor having one end electrically connected with a base terminal of the first transistor, and the other end electrically connected with a first secondary winding of the self-excited transformer; a second resistor having one end electrically connected with a base terminal of the second transistor and the other end electrically connected a second secondary winding of the self-excited transformer; a first regulation diode set electrically connected in parallel with the first secondary winding of the self-excited transformer, wherein a second voltage turns on the first transistor while the first secondary winding sends a feedback current to the primary winding to obtain the second voltage across the first regulation diode set; and a second regulation diode set electrically connected in parallel with the second secondary winding of the self-excited transformer, wherein a third voltage turns on the second transistor while the second secondary winding sends a feedback current to the primary winding to obtain the third voltage across the second regulation diode set, and the second secondary winding and the first secondary winding are of reverse polarity.
Preferably, the power convert further comprises a start circuit comprising: a third resistor electrically connected to one of the DC supply terminals; a first capacitor having one end electrically connected with the other end of the third resistor and the other end grounded; a third diode having a anode end electrically connected with a connecting point of the third resistor and the first capacitor and a cathode end electrically connected with the output end of the power converter; and a bilateral trigger diode electrically connected with the anode end of the third diode and a connecting point of the second regulation diode set and the second resistor.
Certainly, the load can be a discharge lamp.
Preferably, the ballast converter further comprising a resonance circuit electrically connected with the load, wherein the resonance circuit comprises at least one inductor and at least one capacitor for providing a desired current to the load.
Preferably, the resonance circuit further comprises: a second capacitor electrically connected in series with the load; and a second inductor having one end electrically connected in parallel with the load and the other end electrically connected with the other end of the primary winding.
Preferably, the ballast converter further comprises a wave-filter inductor, the wave-filter inductor having one end electrically connected with the input voltage and the other end electrically connected with the rectifier for filtering the input voltage.
Preferably, the ballast converter further comprises a set of charge pump capacitors, the charge pump capacitors electrically connected with a high-frequency end of the load and two ends of the power source for providing a high-frequency current circuit between the load and the input voltage, thereby modifying the valley-current waves of the input voltage to improve the power factor of the ballast converter.
Preferably, the ballast converter further comprises a second energy-storing capacitor electrically connected with the high-frequency end of the load for charging the energy-storing capacitor.
Preferably, the charge pump capacitor comprises a first charge pump capacitor and a second charge pump capacitor, wherein the first charge pump capacitor is electrically connected in series with the second charge pump capacitor, and a connecting point of the set of charge pump capacitors is electrically connected with the high-frequency end of the load for providing a high-frequency current circuit between the load and the input voltage.
Now the foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawings, wherein: